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Use of the 'Equal Area Grid' (Grid_ETRS89-LAEA)

Use the present discussion topic to clarify aspects related to the use and application of the INSPIRE 'Equal Area Grid' (Grid_ETRS89-LAEA).

Definition and properties

The 'Equal Area Grid' is defined in Section 2.2.1 of Annex II of the Implementing Rule as regards Interoperability of Spatial Data Sets and Services.

It is mainly intended for spatial analysis or reporting purposes (e.g. statistical information), but not for communities where the grids have to be optimised for data exchange, supercomputer processing and high volume archiving of new data each day.

Use of the grid

Either the 'Equal Area Grid' or the 'Zoned Geographic Grid' (defined in Section 2.2.2 of Annex II of the mentioned Implementing Rule) shall be used as a geo-referencing framework to make gridded data available in INSPIRE (data provision for INSPIRE), unless:

a) Other theme-specific grid is specified for a data theme;

or

b) For grid referencing in regions outside of continental Europe, where Member States may define their own grid under certain conditions.

In particular, the 'Equal Area Grid' shall be used for pan-European usage in the Statiscal Units data theme (theme-specific requirement).

 

NOTE: Please, look at the following discussion topic in the parent cluster group - where the topic was slightly mentioned.

https://themes.jrc.ec.europa.eu/discussion/view/8899/copernicus-rda-eu-dem-egcs-naming

 

  • Peter STROBL

    Seemingly the use of Grid_ETRS89-LAEA is only encouraged at cell sizes that are integer powers of 10 meters. This could mean that data at other resolutions might have to undergo a coarsening/supersampling by a factor of up to more than 3.

    In particular for orthoimagery (where GRS80 seems not to be a choice) this seems rather impractical.

    Why is there no denser system for Grid_ETRS89-LAEA, like the one for Grid_ETRS89-GRS80, which has 24 levels, ideally one that has somewhat compatible levels in both CRSs?

  • Jordi ESCRIU

    You are right - The levels of resolution of the Grid_ETRS89-LAEA are limited to powers of 10 meters. This may be due to the fact that it was initially thought just for pan-European spatial analysis and reporting, and not for (gridded) reference data.

    These levels do not consider several of the typical resolution levels (LoD) in which elevation and orthoimagery datasets are usually produced and distributed.

    In my opinion, the ETRS89-LAEA projection is not well-suited for reference data. Additionally, there is nothing preventing orthoimagery to be provided in geodetic coordinates (e.g. ETRS89-GRS80), avoiding the use of projections.

    In fact, these aspects led to the proposal of the 'Zoned Geographic Grid' (Grid_ETRS89-GRS80).

  • Peter STROBL

    Fine, then let's continue there wink!

  • Mirosław MIGACZ

    By Mirosław MIGACZ

    The ETRS89-LAEA grid is used by the statistical community for pan-European activities, as described here. An example of its usage is the GEOSTAT project, which results in publishing population data on grids. Details can be found here.

    Also this grid is suggested by Eurostat as a default reporting unit for georeferenced statistical surveys, e.g. Farm Structure Survey.

    As for the grid resolution: The GG specification limits the resolution to powers of ten as stated above. Statisticians need other resolutions (e.g. 250m, 125m, 5km). Therefore in the Statistical Units [SU] specification there is a grid package that allows to define any resolution or reference system - either in the StatisticalGrid feature type or in the StatisticalGridCell cell code.

  • Peter STROBL

    Could you point me to the paragraph/page in the SU specs where that is stated. I would have assumed it under 6.1.4 Grids (p.48/49) but couldn't find it.

    In any case it would give me that freedom only for statistical data, but not for orthoimagery or DEMs. Right?

  • Mirosław MIGACZ

    By Mirosław MIGACZ

    The grid package is described on pages 18-22 of the SU spec (section 5.3.1.2.2.)

  • Peter STROBL

    Thanks! I must admit that I still struggle with the structure of these documents. Anyhow, I couldn’t find a sentence that would explicitly say that the generic requirements for LAEA grids (see p.49) are waived for this theme.
    BTW, I ran into this code example: CRS3035RES100000mN5400000E1200000 and thought I’d seen somewhere the requirement that cell sizes larger than 100m should be denoted in km. Or do I again mix things up?

  • Mirosław MIGACZ

    By Mirosław MIGACZ

    In the Commission Regulation 1253/2013 (implementing rules for annex II & III) we have in theme-specific requirements for SU: (2) For pan-European usage, the Equal Area Grid defined in Section 2.2.1 of Annex II shall be used.

    The SU spec quotes on pages 48-49 the implementing rules in the GG specification (page 7) stating: (1) Other grids may be specified for specific spatial data themes in Annexes II-IV ( < - ANNEX IV? :) ). In this case, data exchanged using such a theme-specific grid shall use standards in which the grid definition is either included with the data, or linked by reference.

    So I guess that means that for pan-European usage SU is forced to use the "power of 10" version of the ETRS89-LAEA grid described in the GG spec, while for any other (country level, local level) grids with other CRS and resolutions may be defined. This doesn't permit using the LAEA grid with resolutions other than the "power of 10" for pan-European usage, I'm afraid and that may be a topic for a change proposal to SU implementing rules.

    As for the cell code example, the SU spec states that the resolution should be provided in meters. However, these are just technical guidelines in the data specification. The only obligatory requirements are those in the implementing rules (Commission Regulation 1253/2013), so I guess there's nothing wrong in shortening the resolution in the cell code to km.

  • Jordi ESCRIU

    Dear Miroslaw,

    When I read "In this case, data exchanged using such a theme-specific grid shall use standards in which the grid definition is either included with the data, or linked by reference", I understand that if an INSPIRE theme allows using other grids different than the ETRS89-LAEA grid (which is the case of SU, as you pointed out) the data provided according such grid shall be accompanied with the grid definition.

    May be I am not understanding your point, but my impresion is that there is no need to change he SU section of the Implementing Rule.

  • Mirosław MIGACZ

    By Mirosław MIGACZ

    Dear Jordi,

    As I see it:

    - Section 2.2.1. of Annex II defines the ETRS89-LAEA grid with cell sizes being the power of ten.

    - SU spec states "(2) For pan-European usage, the Equal Area Grid defined in Section 2.2.1 of Annex II shall be used."

    Therefore, for pan-European usage no grid with a cell size other than power of ten (e.g. 250 m, 5 km) can be defined in the scope of SU.

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Elevation, Ortho & Grids

Elevation, Ortho & Grids

INSPIRE Thematic Cluster Elevation, Orthoimagery, Reference systems, Geographical grids - Join this group to share your knowkledge, learn and collaborate in solving issues related to the Elevation, Orthoimagery, Reference systems and Geographical grids themes